A Study on Distance Transport of PM2.5 to Xianlin in Nanjing, China and its Source Areas

ABSTRACT

With rapid economic development in China, the concentration of particulate matters emitted into the atmosphere has become increasingly higher. As an important city in the Yangtze River delta, Nanjing City in China has a high PM_2.5 concentration level, due partly to the long-range transport of PM_2.5 from elsewhere. It is important to study the transport pathways and PM_2.5 source areas as the results can serve as scientific evidence for prevention of regional air pollution. In this study, we analyzed the 2013–2016 PM_2.5 concentration data at Xianlin in Nanjing City, China. After being clustered to determine the transport pathways, backward trajectory data underwent potential source contribution function (PSCF) and trajectory sector analysis so as to identify potential PM_2.5 source areas. A new index called pollution source strength was proposed to indicate the level of pollution in an administrative region. Our results indicate that the concentration of PM_2.5 at Xianlin in the city and externally sourced PM_2.5 are high in winter, but much lower in summer. The external source areas also show some spatiotemporal regularities. External PM_2.5 source areas lie chiefly to the south and southwest of Xianlin, Nanjing City in spring, but mostly to the southeast in summer, to the southeast and northwest in autumn, and to the northwest and northeast with a broader distribution in winter.